“The next election can’t be fought in the gutter. The most important thing for me was to defend my dad.”

He also told of his family’s shock at the article, which he has denounced as a “lie”, insisting his father “loved Britain” and stressing he would not “back away” in his fight with the Mail.

“You learn in this job that you have to do the right thing and stand up to the strong,” he added.

But a senior Daily Mail executive defended the article on Ralph Miliband, a Jewish refugee who fled to Britain to escape the Nazis and who served in the Royal Navy during the Second World War.

Deputy editor Jon Steafel made clear that the paper stood by the article – which first appeared on Saturday – arguing that Ralph Miliband’s writings showed that he was “very antipathetic” to the views and values of many British people.

“His views on British institutions from our schools to our royal family to our military to our universities to the church to our great newspapers ... what he said was that he felt that all of those things were bad aspects, were unfortunate aspects of British life,” he said.

“If you take those things together and you combine them with an espousing of a Marxist ideology, that in our view represented someone who hated British values.”

Mr Steafel insisted it was reasonable for the paper to highlight his views as he had played an important role in shaping his son’s outlook and opinions.

But he accepted that the publication of a photograph of Ralph Miliband’s grave alongside the online version of the article had been an “error of judgment” and that it has been removed when the Labour leader complained.

Mr Miliband, who has stressed that he does not share his father’s Marxist ideology, can expect strong attacks by the Right-wing press ahead of the 2015 election.

Former Conservative Cabinet
minister Lord Heseltine has also criticised the Daily Mail.

He told BBC2’s Daily Politics:
"This is carrying politics to an extent that is just demeaning, frankly.
The headline isn't justified. It is completely out of context. As
everybody knows the guy fought for this country and we now live in a totally
different world to the clash between communism and fascism."

But Education Secretary Michael
Gove stressed: “Newspapers shouldn’t apologise to politicians for being
robust..that’s the price we pay for liberty”

Mr Gove though also said he understood Mr Miliband’s
decision to defend his father.